Studies are proposed to determine the effects of dietery fats on chemical induction of colon tumors in rats and to evaluate the contribution of several different mechanisms by which diet may influence chemical carcinogenesis. Tumor incidence and latent period will be measured in Male Sprague-Dawley rats fed 12 or 46% of calories as predominantly saturated (beef tallow), unsaturated (corn oil) or partially saturated (crisco) fat and treated with 1,2 dimethylhydrazine (DMH) or N-methyl-N-nitrosourea (NMU). Possible mechanisms of dietary effects will be examined by quantitation of hepatic and colonic mucosal mixed function oxidase, cytochromes P450 and P448, NADPH cytochrome c reductase, cellular kinetics of colonic mucosa and humoral and cellular immunity and by examination of DMH metabolism in vivo and in vitro using rats treated by the same dietary and chemical methods. The results should confirm and extend knowledge of effects of dietary fat on colon tumor incidence and provide at least partial explanations of the means by which fat exerts its effect.